Medical Tests

Wound Drainage Culture

What It Is

A wound drainage culture is a test to detect germs such as bacteria, fungi, or viruses in an open wound or abscess (boil). Open wounds, in which the skin has been torn, cut, or punctured, can result from things such as falls, bites, or burns. A surgical incision is also a type of an open wound.

Germs can infect wounds and cause pain, swelling, warmth, and redness around the wound. Infection can also lead to pus — a yellowish, foul-smelling fluid — building up and draining from the wound. Drainage can be obtained from an abscess under the skin after it is lanced.

Wound drainage cultures can show what type of germ is causing the infection and help determine which treatment is most appropriate.

Why It's Done

Doctors order wound drainage cultures when they suspect that wounds have become infected. Symptoms of infection may include:

pain, swelling, warmth, or redness around the wound

drainage of foul-smelling fluid or pus

fever

general ill feeling if the infection has spread or has been present for a while

Preparation

You don't have to do anything special to prepare your child for a wound drainage culture, although you should tell the doctor about any antibiotics your child is taking or has taken recently, as this can affect the results.

A doctor or nurse will clean the surface of the wound and the surrounding skin with a sterile solution such as saline.

Procedure

There are several methods of obtaining a wound drainage culture:

The most common method involves pressing the tip of a sterile cotton swab into the wound and gently rotating it to collect a sample.

Another method is withdrawing pus or fluid from the wound with a syringe and a small needle. This is called needle aspiration.

The skin over an abscess might need to be cut to reach the pus inside. This is known as incision and drainage. The cut is usually small.

The culture sample will be placed in a special container and sent to a laboratory where it will be observed for 2 days to see if any germs grow.

After any of these procedures, the wound is cleansed and bandaged.

What to Expect

If an abscess needs to be punctured or a slit has to be made in the skin, numbing cream will be placed over the skin about 30 minutes before the procedure. Your child may feel pressure and some discomfort during the incision and drainage, but there shouldn't be any pain.

An infant or toddler may receive medication by mouth or through a vein to make him or her sleep during the procedure.

Getting the Results

A technician with expertise in interpreting culture samples will look at any germ growth under a microscope and may run some chemical tests, then report the results to your child's doctor, who review the results with you. If nothing significant grows, the culture is called "negative." If a germ that can cause infection grows, the culture is "positive."

Results aren't available to the patient or family at the time of the test, and are usually ready in 2 days, because it takes time for the germs to grow. Some less common kinds of germs grow slowly and may take several weeks to become obvious in the container.

If the wound looks infected or your child looks ill, the doctor may start treatment before the final results are ready. Treatment will be based on the most likely cause of infection, but can be revised to be specific for the germ found when the culture is completed and the most effective treatment has been determined.

Risks

A wound drainage culture is a safe procedure. There may be some mild bleeding after the wound is swabbed or the skin is cut. Most of the time, there are no complications.

If your child requires sedation, there's a slight chance of slowed breathing due to the medications. If there are any problems with the sedation, the medical staff will treat them right away.

Helping Your Child

You can help prepare your child for a wound drainage culture by explaining that the test will be brief. It's important to tell your child to be still during the wound drainage collection.

If an abscess is going to be drained, you can tell your child that the discomfort will be brief. Explain the procedure in simple language, and make sure the child understands where on his or her body the culture will be performed. After the procedure, make sure your child follows any other instructions the doctor gives you.

If You Have Questions

If you have questions about the wound drainage culture, contact your doctor. You can also talk to the nurse or doctor performing the procedure right before it's done.

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Seattle Children’s provides healthcare without regard to race, color, religion (creed), sex, gender identity or expression, sexual orientation, national origin (ancestry) or disability. Financial assistance for medically necessary services is based on family income and hospital resources and is provided to children under age 21 whose primary residence is in Washington, Alaska, Montana or Idaho.